The present invention relates generally to chemical compositions for use as topical anesthetics or skin refrigerants. More specifically, this invention provides chemical compositions for use as topical anesthetics or skin refrigerants, which compositions do not cause the depletion of the stratospheric ozone layer and are non-toxic. Even more specifically, this invention provides chemical compositions for use as topical anesthetics or skin refrigerants, which compositions, in addition to having the above properties, match the skin temperature versus time profile needed, in the management of myofascial pain syndromes, for effectively freezing skin prior to minor skin surgery and for effectively freezing skin for giving painless injections.
The term vapocoolants will be understood to include topical anesthetics, skin refrigerants and the like. Vapocoolants are volatile liquid compositions which exert high pressure in a container at room temperature. When a container having such compositions is inverted and opened, in the proximity of human skin, the liquid is immediately expelled out of the bottle in a stream and starts evaporating. The evaporation of the liquid cools the liquid stream by the time it impacts the skin. The liquid on the skin continues to evaporate and remove heat from skin resulting in the rapid decline of the skin temperature.
The above-described effect of skin cooling is well known in the art. U.S. Pat. No. 4,865,028 to Swart et al. issued Sep. 12, 1989 describes a method for the therapeutic treatment of the skin of a human or animal by the freezing of the skin by application of a refrigerant thereto wherein the refrigerant is applied through a cotton wool bud which encompasses the discharge end of the supply tube and which cotton wool bud surrounds the outlet of the supply tube. In fact, the ""028 patent lists several refrigerants which may be suitable for use in the method of the ""028 patent. In this regard, several hydrofluorocarbons are disclosed such as tetrafluoromethane, trifluoromethane, hexafluoroethane, monobromotrifluoromethane, and 1,1-difluoroethane. It is also mentioned in the ""028 patent that all of these listed hydrofluorocarbons are xe2x80x9coften environmentally harmful.xe2x80x9d Thus, the ""028 patent in fact points away from the use of 1,1-difluoroethane (152a).
However, when the ""028 patent refers to the environmentally deleterious effects of hydrofluorocarbons (HFC""s) the reference is to effects such as the greenhouse effect. It is well known that hydrofluorocarbons or HFC""s have no ozone depletion potential whatsoever. On the other hand, compounds such as hydrochlorofluorocarbons (HCFC""s) and chlorofluorocarbons (CFC""s) are considered to be ozone depleting.
In fact, vapocoolants have been on the market since the 1940""s and have been known since that time. The most widely used commercial products are Fluorimethane(copyright) (The Gebauer Company, Cleveland, Ohio) and ethyhlchloride. Fluorimethane(copyright) is used for management of myofascial pain syndrome using the well-known spray and stretch technique (See Manyel J. M.: xe2x80x9cSpray and Stretch treatment for myofascial painxe2x80x9d; Hospital Physician, 1973). Ethylchloride is used for pain control in pain associated with injections or contusions. While it is acknowledged that vapocoolants in general have been on the market since the 1940""s, the present invention is directed to the specific development of chemical compositions which are non-ozone depleting and non-toxic, while at the same time having a skin temperature-time profile similar to that obtained upon application of the currently widely available products such as Fluorimethane(copyright) and ethylchloride.
The ""028 patent also discloses in its specification, Dutch patent application No. 7,308,008, wherein the use of a liquid refrigerant with a low boiling point for carrying out cryosurgical treatments, such as the removal of an eye lens affected by cataract and cataract operation is disclosed. However, the use of compositions of the present application is not for cryosurgery, but for the specific applications included herein.
U.S. Pat. No. 5,039,485 issued Aug. 13, 1991 to Conviser et al. discloses a sterilant mixture comprising 14-25 mole percent ethylene oxide and 75-86 mole percent 1,1,2,2-pentofluoroethane, and a sterilization method using the same. The ""485 patent is relevant in that it recognizes the problem associated with the use of CFC""s, i.e., the resultant damage to the stratospheric ozone layer. It is also disclosed in the ""485 patent that 1,2,2,2-tetrafluoroethane (HFC 134a), does not increase the ozone depletion potential of a certain sterilant mixture.
The currently marketed vapocoolants described above (Fluorimethane(copyright) and ethylchloride), are intended for topical application in the management of myofascial pain, restricted motion, muscle spasms and for the control of pain associated with injections. Fluorimethane(copyright) is classified as a prescription drug and is regulated by the United States Food and Drug Administration (FDA). It was formulated by Dr. Janet Travell in the late 1950""s and since then has been widely used for the management of the above conditions and symptoms. It is a mixture of two CFC""s, namely dichlorodifluoromethanexe2x80x9415% and trichloromonofluoromethanexe2x80x9485%. Chlorofluorocarbons are known to be extremely harmful to the stratospheric ozone layer and in accordance with the Montreal Protocol of September 1987, have to be phased out along with all other CFC""s by the year 2000. The present invention offers new chemical compositions that match the skin temperature-time profile of Fluorimethane(copyright) and ethyl chloride, which compositions do not contain CFC""s and which are non-toxic.
Ethylchloride has been found to be carcinogenic, hepatotoxic and is also known to be highly flammable. The present invention makes it possible to replace ethylchloride with a non-ozone depleting vapocoolant which shows the temperature time characteristics of ethylchloride and Fluorimethane(copyright) and which is simultaneously non-toxic and non-carcinogenic in comparison to ethylchloride. The present chemical compositions are also not as flammable as ethyl chloride.
It is a primary object of the present invention to provide a chemical composition for use as a vapocoolant, which vapocoolant does not cause the depletion of the stratospheric ozone layer and which is non-toxic.
It is another object of the present invention to provide a vapocoolant having the above described characteristics and which has a skin temperature versus time profile suitable for management of myofascial pain syndromes, for effectively freezing skin prior to minor skin surgery and for effectively freezing skin prior to giving painless injections.
It is a further object of the present invention to provide chemical compositions which have similar skin temperature versus time profiles as compared to currently available vapocoolants for similar purposes.
It is yet another object of the present invention to provide chemical compositions which are non-toxic in comparison to ethylchloride.
A still further object of the present invention is to provide chemical compositions for the purposes described above and having the characteristics described above, which compositions are not carcinogenic.
A further object of the present invention is to provide chemical compositions for the above described purposes and having the above described characteristics, which compositions are less flammable than ethylchloride.
Yet another object of the present invention is to provide chemical compositions for the above described purposes and having the above described characteristics, so as to be effective in replacing the presently used chlorofluorocarbon vapocoolants, which CFC""s are to be phased out by the year 2000.
In accordance with the invention, there is provided a non-ozone depleting, non-toxic and non-carcinogenic vapocoolant liquid chemical compostion for use in localized cooling of a desired area of the skin of humans and other animals, said composition comprising by total weight of the composition 40 to 55% hydrofluorocarbon and 60 to 45% of ethyl alcohol; and being capable of cooling said desired area to at least as low as approximately minus 5xc2x0 C., upon spraying of said composition onto said desired area, from a predetermined distance for a maximum of 5 seconds.
While the invention will be described in connection with a preferred embodiment, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.